Research

Saltmarsh Nitrogen Cycling

Estuaries, where freshwater mixes with the oceans, are unique and important environments serving as storm barriers, critical habitat for wildlife, and economically valuable fisheries. Nutrients carried into the oceans by rivers are vital to the health and productivity of estuaries. However, surplus nutrient supply from human sources is known to cause excessive growth of algae leading to fish kills and habitat degradation. Rivers commonly flow through a system of estuarine marshes before reaching the ocean. These marshes act as enormous biological reactors in which nutrient loads are altered. Therefore, studying the fate and balance of nutrients in coastal marshes is essential to understanding the function of estuaries.

The goal of our project is to study nitrogen cycling in marsh sediments of the Apalachicola National Estuarine Research Reserve (ANERR), Florida. The ANERR encompasses a productive and pristine ecosystem where the Apalachicola River reaches the Gulf of Mexico. Pristine beaches, beautiful scenery, abundant oysters, fish, manatees, dolphins, and migratory birds make the Apalachicola Bay a valuable resource and attractive recreation destination. Future water reallocation and the potential for modified nutrient loading as a result of land use change in the Apalachicola River watershed threaten to alter the productivity of Apalachicola Bay. Prior to reaching the ocean, the Apalachicola River forms a network of distributaries and flows through an extensive system of low-salinity marshes at the boundary between the River and the Apalachicola Bay. These marshes are the main target of our research program.

Our work at the FSU Coastal and Marine Laboratory involves the study of long-term nitrogen loss via denitrification (nitrogen gas production by microorganisms) and nitrogen burial in marsh sediments. Nitrogen transformation is also being studied in shallow, permeable sands of Apalachicola Bay and the Gulf of Mexico. Controlled environment chambers at the FSUML are used to incubate sediment cores during denitrification rate measurements. This research is being conducted with financial support from the NOAA Estuarine Reserves Division, graduate fellowship program for Thomas Gihring, a graduate student in Dr. Kostka's laboratory.